The present invention relates to non-asbestos type friction material applicable for various friction materials (pad, lining, clutch facing, brake block, etc.).
So far, for the non-asbestos type friction materials, aramid fibers have been used commonly as organic fibers (example: U.S. Pat. No. 4,374,211). In the case of particularly drum brake lining among them, however, the formulation rate of organic materials becomes higher over that in the case of asbestos type lining, thus a larger torque (initial peak) is prone to generate initially causing a problem of instability of efficiency. Moreover, in the case of non-asbestos type lining, as a substitute for asbestos, a combination of aramid fibers, metallic fibers, inorganic fibers, etc. is used ordinarily for base materials and, because of high content of inorganic materials for the improvement in heat resistance, the noise property is also called into question.
As a result of extensive investigations in view of this situation, a non-asbestos friction material with improved stability of initial efficiency and with improved noise property has been developed by the invention.